Adapting the FBG cavity sensor structure to monitor and diagnose PD in large power transformer

Fiber optics vibration sensors have been extensively studied over the last ten years they have mainly been used to capture low frequency signals. One of these investigations has been commercialized to measure and trend End Winding Vibration (SEW) inside larger power generators. This sensor consists of a twin grating cavity and can be used to monitor temperature change as well as vibration. This paper will discuss the adaptation of the FBG cavity structure into a broad band sensor capable of measuring a range of higher frequencies previously identified as PD signals in the transformer from 30K to 300 KHz. Other work has been done to explore the possibility of developing a fiber optics acoustic sensor. The incentive is to overcome the limitation of the resonant based, acoustic, piezoelectric PD sensors previously used to analyze and locate PD. Working in resonance, they are unable to reveal the detailed spectrum or the signature of the PD events. We want to improve the packaging material and structure, then optimize the coupling methods to enhance its signal to noise ratio. All our work is still based on the fiber gratings cavity structure.